In recent years, much attention is paid to a silicon carbide semiconductor device using silicon carbide (SiC) as a next-generation semiconductor device which can achieve high breakdown voltage and low power loss. When compared with silicon (Si) which has been used in a conventional semiconductor device, SiC is about ten times higher than Si in dielectric breakdown electric field strength. Therefore, a silicon carbide semiconductor device is expected to be applied particularly to a power semiconductor device which requires high breakdown voltage.
There exists a p-n junction diode as one of power semiconductor devices with high breakdown voltage. In a conventional SiC p-n junction diode, a mesa structure is formed at an anode portion for element isolation and relaxation of electric field concentration at the anode end (for example, Patent Document 1). Further, there is a conventional SiC p-n junction diode whose mesa structure is formed not vertically but obliquely (for example, Patent Document 2). Also, it is known that, by forming a P-type electric field relaxation layer at a mesa peripheral portion, a depletion layer is formed at the p-n junction between an N-type layer and the electric field relaxation layer in the silicon carbide semiconductor, and that an electric field in an off-state of the silicon carbide semiconductor device, namely, in a static state where constant voltage is applied, is suppressed (for example, Patent Document 2).